Encapsulated circuit modules are known.
Encapsulated circuit modules include a substrate having wiring (such as a printed wiring board), electronic components mounted so as to be electrically connected with the wiring of the substrate, and a resin covering the substrate together with the electronic components. By covering the electronic components with the resin, encapsulated circuit modules can provide protection for electronic components and protection of electrical contacts between the electronic components and the wiring of the substrate.
Encapsulated circuit modules include electronic components as described above. Some electronic components are vulnerable to electromagnetic waves. Other electronic components emit electromagnetic waves.
In many situations where an encapsulated circuit module is actually used, the encapsulated circuit module is combined with other electronic components. Such other electronic components may be included in another encapsulated circuit module or not. Moreover, some other electronic components are vulnerable to electromagnetic waves and others emit electromagnetic waves.
When the encapsulated circuit module is actually used, it may be desired in some cases to reduce the influence of the electromagnetic waves emitted by other electronic components outside the encapsulated circuit module on the electronic components included in the encapsulated circuit module. It may also be desired in other cases to reduce the influence of the electromagnetic waves emitted by the electronic component(s) included in the encapsulated circuit module on other electronic component(s) outside the encapsulated circuit module.
From such a viewpoint, for circuit modules without having been subjected to encapsulation with a resin, a technique of surrounding the entire circuit module with a metal shield against electromagnetic waves is practically used.
An exemplified metal shield is a box formed of a thin metal plate, with one side open. When using a box, the circuit module is not usually encapsulated with a resin. The box is attached to the substrate with the edge defining the opening of the box being in contact with the substrate to enclose the electronic components and thereby to shield the electronic components.
Another technique has been suggested for encapsulated circuit modules in which a metal shield layer is formed on the surface of the resin used for encapsulation by applying a paste containing metal powder to the surface of the resin or plating such surface with a metal using a dry or wet process. The process of applying a paste and a sputtering process, which is a kind of a dry metal-plating, have been practically used.
Techniques using a box as described above or techniques of forming a shield layer by applying a paste containing metal powder to or metal-plating a surface of a resin is for preventing the electronic components located inside and outside of the encapsulated circuit module from affecting each other by electromagnetic waves.
In some cases, however, a single encapsulated circuit module has electronic components that mutually affect by electromagnetic waves. For example, if an encapsulated circuit module has two or more electronic components and one of them is a high frequency oscillator, strong electromagnetic waves are emitted by the electronic component which is a high frequency oscillator. In such a case, if another electronic component in the encapsulated circuit module around the electronic component which is a high frequency oscillator is the component of which normal function is badly affected by strong electromagnetic waves, it is necessary to protect that other electronic component from the electromagnetic waves emitted by the electronic component which is a high frequency oscillator. The techniques using a box as described above or techniques of forming a shield layer by applying a paste containing metal powder to or metal-plating a surface of a resin are merely directed to form a wall to shield electromagnetic waves outside the circuit module or the encapsulated circuit module. If a single encapsulated circuit module has electronic components that mutually affect by electromagnetic waves, the wall does not function to reduce such mutual influence.
When a single encapsulated circuit module has electronic components that mutually affect by electromagnetic waves, as a technique to reduce such mutual influence by the electromagnetic waves, techniques of providing a partition member made of a metal capable of shielding electromagnetic waves in the encapsulated circuit module have been used. The partition member has a wall extending upward from the substrate and, in some cases, a roof connected to the wall. Side edges of the wall (the term “side edges” as used herein refers to both ends of the wall in the direction parallel to the substrate) are typically in contact with the side surface of the resin covering the electronic components of the encapsulated circuit module and the upper end or the roof of the wall is typically in contact with the surface of the resin covering the electronic components of the encapsulated circuit module.